The Study Of Photics Character And Thermoelectrical Properties Of Silicon-Germanium Alloys

This paper includes two parts of work: one is the FT1R spectroscopy of SiGe alloys, the other is the relation of the Ge concentration and the thermoelectrical properties.CZ-Si single crystals with high concentration Ge-doped were measured by Fourier transform infrared spectroscopy (FTIR) at room temperature (RT) and 10 K. The oxygen concentration decreases with increasing the concentration of Ge. The shift of the peak of 1106 cm-1 to lower wave numbers and the appearance of a new peak at the wave number of 1118 cm-1 (at 10 K) are attributed to Si-O-Si vibration perturbed on Ge atoms at second and third neighbor sites with changing coupling strength. New peaks appeared at the wave number of 710cm-1 and 800cm-1, which became clearer with an increase in Ge concentration. And the absorption strength and wave sharp of these peaks are similar at RT and 10 K. Make use of the peak that appears at the wave number of 710 cm-1, the relation of absorption coefficient (amax), half-peak breadth (W1/2) and Ge concentration is determined. The formulas of determining Ge concentration in CZ-Si single crystals by means of FTIR technology have been given at RT and 10 K, respectively:Investigated the Seebeck coefficient, thermal conductivity and electrical conductivity were investigated of SiGe alloys. The Seebeck coefficient with the absolute maginitude of 200-500 μV/K in the whole temperature range was investigated. The Seebeck coefficient of p-SiGe alloys with <111> orientation was around 325-400 μV/K, while that of the sample with <100> orientation was around 450-530 U.V/K. The anisotropy appeared to attribute to the difference in crystallographic direction. The thermal conductivity depended greated on the alloys composition due to the phonon scattering at point-like defects, and decreased with an increase of temperature. The electrical conductivity of alloys was well controlled by suited doping and showed granual decrease against temperature. It was originaing in the decrease of the carrier mobility. The dimensionless figure of merit 0.0354 was evaluated in SiGe single crystal at 673 K. By suitable control of both the dopant impurity concentration and the alloys composition, a large capability of single crystal SiGe alloys is expected.